Overhead projector
OwnerPeter H. Grunwaldinventor
Life of this patent
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Abstract
In an overhead projector comprising a writing plate, and under this arranged Fresnel lens, a light source and an objective carried by a carrying arm, the problem to be solved is to overcome the disadvantages of the state of the art and to provide a possibility for a lecturer to make information retrieved from an electronic information source, for example, a computer or an electronic game, accessible to a large viewer and listener circle. The invention solves this problem thereby, that between the Fresnel lens and the writing plate there are arranged a layer of liquid crystals which are aligned in an electric field and transparent electrodes on both sides thereof, whereby two of the plates or films traversed by the light beam have light polarizing properties.
Claims18
An overhead projector comprising a base, a transparent writing plate supported on said base, a light source, objective lens and reflector supported above said writing plate, a Fresnel lens disposed below, parallel to and spaced from said writing plate, a reflector below said Fresnel lens, a layer of light deflecting liquid crystals sandwiched between said writing plate and said Fresnel lens, transparent electrodes on opposite sides of said layer of liquid crystals, a frame holding together as a unit said writing plate, Fresnel lens and liquid crystal layer and said electrodes, and terminal contacts for said electrodes in said frame.
In an overhead projector having a base, a light source and a projecting lens, an assembly comprising a transparent writing plate, a Fresnel lens parallel to and spaced from said writing plate, a reflector below said Fresnel lens, a layer of liquid crystals sandwiched between said writing plate and said Fresnel lens, transparent electrodes on opposite sides of said layer of liquid crystals and a frame surrounding and holding together as a unit said writing plate, Fresnel lens, liquid crystal layer and electrodes, said frame being hollow and containing electronic components for actuating said electrodes, said assembly being removably received on and supported by said base.
Dependencies are inferred from the claim text.